Crystal Morphology of Hydrogenated Castor Oil in the Crystallization of Oil-in-Water Emulsions: Part II. Effect of Shear

Abstract

Crystallization of hydrogenated castor oil-in-water emulsions has been studied by polarized light microscopy under controlled shear. Shear rates from 0 to 100 s–1 have been applied at cooling rates from 1 to 5 °C/min. Emulsions have been redispersed by shear before crystals formed. The higher the shear rate, the smaller the droplet size. Nucleation has been promoted with the increase of shear rate. Morphology analysis indicates that crystals in the form of fibers favor gentle shear, i.e., 1 s–1, but fibers can be broken up with the increase of shear time. Crystals as rosettes tend to become elongated in the flow direction. At lower cooling rate (<2 °C/min), mean crystal size decreases with shear rate.